System and method for exception handling in dynamically linked programs

Abstract

A compiler requires normal exceptions that are throwable by a method to be either explicitly declared or else 'caught' by appropriate exception handlers in the method to be compiled. This ensures that all normal exceptions thrown will be handled by a programmer specified exception handler. The compiler inspects all instructions in a specified method that throw exceptions and all instructions that invoke other methods, and determines whether each type of exception throwable by those instructions and invocable methods is (A) a serious exception (i.e., not a normal exception), (B) is caught by an enclosing exception handler, or (C) is explicitly declared in the method header of the specified method. If any throwable exception cannot be so categorized, that means the throwable exception is a normal exception that is not caught by an enclosing exception and is not explicitly declared in the method header, which means that the method to be compiled is not well formed. As a result, the compiler rejects the specified method, aborting compilation and generating an appropriate error message. The compiler determines the set of throwable exceptions in part by inspecting the methods that are invocable by the specified method for declarations of throwable exceptions. When initiating execution of the specified method, the program execution system inspects the method's declaration of throwable exceptions and blocks execution of the specified method unless exception handlers have been established for handling all the exceptions, if any, included in the declaration.